On the March/April newsletter, and on their web site, basic miles on AC can qualify for EP/GOLD on CP. There is no mention whether the flights can go towards requalifying. That's important for me as I do a lot of short trips on discount tickets. I could never qualify based on miles.
For the lounge, if EP or GOLD or Empress member, you and a guest are able to use either lounge. I too am interested in AA access as I have award tickets in business class for a journey in August.